InternetNews talks to developers and vendors about the rise of Btrfs as a successor to Ext4. Though Ext4 adds extents, Chris Mason, Btrfs developer noted that BTRFS adds a number of other features beyond that. Among those features are items like snapshotting, online file consistency checks and the ability to perform fast incremental backups. BTRFS (pronounced better FS) is currently under development in an effort led by Oracle engineer Chris Mason. With the support of Intel, Red Hat, HP, IBM, BTRFS could become the engine that brings next generation filesystem capabilities to Linux.

Even when it reaches v1.0, BTRFS will be far behind ZFS.
Just look at the features.
Also there are no current plans for transparent compression on BTRFS, and I consider that a must for many cases.
Not to mention the ZFS syntax is so dead plain simple.
Not so for BTRFS.
I run ZFS on Linux (for a long time now!) via FUSE, and I'm very happy with it